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Wednesday, 19 December 2012

The Regress Argument Against the Language of Thought Hypothesis

This objection has plagued the Language of Thought hypothesis (aka LOTH) since it's very conception. In fact Jerry Fodor included a reply to such objections in his 1975 book the Language of Thought, however these objections have refused to go away. It dubious whether such objections to the Language of Thought hypothesis do in fact under the hypothesis. Many of the supporters of LOTH often appeal to the idea of a language of thought to explain a number of things about our natural languages. For example the language of thought has been appealed to in order to explain the following:

How natural languages (i.e French, English, Russian etc.) are learned

How our natural languages are to be understood

And finally how utterances in a natural language can be meaningful

There are couple of instances in Fodor (1975) which empathize the points above. For example Fodor claims that natural languages are learned through a process of forming and confirming hypothesis regarding the translation of sentences in natural language into mentalese sentences. The LOTH gives us a representational medium in which the representation of the truth conditions of natural language sentences can occur. The Language of Thought theorist further posits that our natural languages are understood because such understanding consists in the translation of our standard natural language sentences into sentences in mentalese. Again sentences in our standard natural language are taken to meaningful in virtue of the meanings of the corresponding mentalese sentences. Simon Blackburn (1984) has claimed that either explanations of this kind lead to an regress as we ought to have to give an explanation of how a language of thought is learned, or that they are simply gratuitous because if it is possible to give a successful explanation which doesn't lead to regress, we ought to have given such an explanation for our natural languages without positing a language of thought at all. Fodor's response to such objections can be found in Fodor (1975) and goes roughly as follows:

The Language of Thought is innate it is not learned.

The Language of Thought is understood in a different sense to how we understand our natural language comprehension.

That sentences in a language of thought are not meaningful in virtue of another meaningful language but rather in a completely different way.

While Fodor's replies to the regress argument aren't totally plausible and may not convince everyone. But Laurence and Margolis (1997) have pointed out that the regress argument against LOTH (at least in the form that Blackburn presents it) relies on the assumption that the language of thought is only posited to explain certain facts about natural language acquisition and natural language comprehension. If it can be shown that there is other empirical phenomena for which the LOTH provides a good explanation then the hypothesis is not gratuitous in the way Blackburn suggests. In fact there does seem to be a good deal empirical evidence that can be best explained by positing a LOT (consider both the systematicity and productivity argument).